const
  max = 50; { max. number of nodes - user may modify}

type

treelement = integer;{user may modify}

  treenode = record
    left,
    right: integer;
    element: treelement;
  end;

  treeforest = record
    a: integer;  { "available" chain }
    space: array[1..max] of treenode;
  end;

  tree = integer;

procedure visit(var out:text; e:treelement);
{+--- on entry  tree has been defined, element e exists
 |    on exit   treelement e is printed legibly to 'out'
 +---------------------------------------------------------}

begin
write (e:4);
end;

.